Pickling of metal pieces



July 23, 1935; I o o s 2,008,781

Filed Aug. 29, 1933 "M L DI M/ 1W 0 Y A mmw W E ,1

w I I! F W "mu w II N m p Patented July 23, 1935 PATENT OFFICE 2,008,781 momma or METAL rIEoEs James R. Bottoms, Butler, Pa., assignor to The American Rolling Mill Company, Middletown, Ohio, a corporation of Ohio Application August 29,

8 Claims.

My invention relates to pickling of metal pieces by the batch method, as distinguished from the method in which sheets, or the like, are connected together to form a band and passed in this form through a pickling tank by the socalled continuous method. An object of my invention is to simplify the method of pickling, as well as the nature and quantity of apparatus required. An object of my invention is to permit the use of inexpensive pickling equipment, such as wooden racks or crates, and to do away with the necessity of complicated and expensive means for holding the sheets separated during the pickling process. Another object of my invention is to eliminate the necessity of metallic pickling racks, separators and the like so as to permit the use of pickling reagents which would otherwise attack such devices.

These and other objects of my invention, which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that novel procedure and by that specific arrangement of parts of which I shall now describe an exemplary embodiment, it being understood that this is not a limitation upon my invention.

In the drawing hereto appended I have illustrated in part section a pickling tank of a. type in which my invention may be practiced together with a load or batch of sheet metal assembled therein for pickling in accordance with the teachings herein set forth.

In the particular exemplary embodiment here inabove referred to I shall treat of the production of so-called etched sheets for enameling use, since my invention is of more than usual utility in connection therewith; but it will be understood that my invention is not limited to this set of circumstances or utility, but is applicable to the pickling in general, not only of sheets, but also of metallic shapes.

In the manufacture of metal designed for enameling use, it is desirable to give to the finished sheets a pickling or an etching treatment resulting in a chemical attack on the grain bgundaries in the surface of the sheets so as to produce a rough or toothed surface, which has superior bonding properties with enamels to be'applied thereto. It appears, for reasons which are not entirely clear, that this etching treatment cannot be satisfactorily carried on in a continuous pickling device. As a consequence it has been the practice to employ the so-called batch picklers. In the conventional method of batch pickling, the sheets are loaded on edge into bronze 1933, Serial No. 687,367

or Monel metal crates. The crates generally comprise a bottom platform member having a series of perforations or sockets into which may be fitted vertically extending bronze or Monel metal pins, which serve not only to hold the sheets in an upright position, but also to separate sheets or groups of sheets one from the other soas to permit the pickling solution to get at the surfaces thereof. The method of loading is to lean a small number of sheets, say 10 or 15, 10 against an outer row of pins. Then a second row of pins is inserted, and a second load of sheets leaned against that. This procedure is continued until the crate isfull.

This procedure is followed in ordinary batch 15 pickling with success, but it has the disadvantage of requiring expensive crates and pins, and of requiring frequent repairs and replacements. There results a very rapid destruction of the crates and pins, and an enlargement of the pin 20 receiving sockets in the crates, so: that the pins no longer fit therein. The eating away of the crates results also in the contamination of the etching solution with salts of nickel and copper. These have a tendency to plate out upon the surface of 25 the steel or iron sheets. It has been ascertained that certain of these metals have a deleterious effect upon enamel subsequently applied to the sheets. I have been unable to find a suitable metal for pickling crates to be used in so-called 30 etching solutions, and a final resort was made to the use of heavy oak crates.

, Considering the cost of wooden crates, their serviceability is fairly satisfactory, but it is not practicable to fit metal pins to wooden crates, 5 since they soon become loose. In order to give wooden pins sufiicient strength it was found necessary to make them large in diameter. This reduced the available space in the crate, and correspondingly increased the tonnage of sheets in 40 the load. Moreover, the wooden pins not only were relatively expensive, but they frequently became broken, causing spilled loads and serious delays.

Briefly, in the practice of my invention, I do away with the necessity of pins or other separating devices, and pile the sheets horizontally with a suitable separating medium there-between. I may use either metal or wooden crates, but preferably the latter if highly corrosive pickling or etching agents are to be used, and I place between the sheets a suitable separating medium in gran-- ular form. In the practice of my invention, the number of sheets which can be loaded upon a single crate has been doubled, and thecapacity of the etching unit has been raised from 3 tons per hour to 7 tons per hour. The expense of the pins and the trouble and delays caused by breakage have been entirely eliminated.

I have discovered that a relatively fine, granular substance, chemically inert to the action of the pickling or etching solution, may be successfully used in thin layers as a separator between sheets. I have found that the pickling or etching proceeds as rapidly as if the sheets were handled individually, and with entire uniformity. The acid appears to be drawn into the interspaces between the grains of the grannular substance so that all portions of the sheet are simultaneously attacked; and no trouble is had with imperfectly etched or pickled areas due to the contact of sheets with each other, or with portions of the pickling mechanism. While any inert, granular separating substance may be employed, I have had excellent results with and prefer to use a clean silica sand. This material is cheap and inert. There is no particular limitations upon the size or fineness of the material, it being suflicient if an inert material is chosen which will adequately support the sheets without shifting, and which as a layer, is porous and pervious to the chemical reagents.

I prefer-to load a crate by positioning a sheet thereon, spreading over said sheet a relatively thin layer, say fith of an inch, or slightly greater, of fine, clean silica sand. The' next sheet is placed upon this separating layer and a second separating layer applied thereto. The stacking of sheets and separating substance is continued in this way until the crate has been loaded to the desired capacity. Then the crate is placed by the ordinary mechanisms for the purpose in a suitable batch picking tank, where the picking proceeds with or without the usual agitation, as desired. When the pickling or etching has been accomplished, the sheets are rinsed in water while in the crate, and then are preferably fed singly through a scrubbing and drying unit. I have illustrated in the drawing a portion of a pickling device of the type of the so-called Cook pickler, having a tank I, containing the pickling or etching reagent I have shown a crate 3 of wood, upon which the sheets 4 are stacked horizontally, the sheets being held apart by the seperating substance which I have hereinabove described, this substance being contained in the interspace 5 illustrated between the sheets. The crate may be supported by suitable hangers 6 and 1, suspended from a truss or bridge 8. The arms of the pickling machine are shown at 9 and I0. These arms serve not only to lower the crate and its suspending mechanismv into the tank, or withdraw it therefrom, but also, if desired, to impart to the crate in,the tank, whatever agitation is deemed to be desirable. The crate 3 may be provided with peripheral pins or abutment devices I I to hold the sheets in position, but these may, if desired, be omitted. There is, in any event, no necessity for pins between the sheets, nor is there any tendency for the sheets to topple over upon the breakage of one or more pins.

Some of the separating sand may be lost during agitation; but this is of minor consequence. It may easily be separated from the pickling reagent, and reused or discarded, as desired, and in no event does it tend to aflect the chemical action of the pickling solution.

It will be understood that modifications may be made in my invention without departing from the spirit thereof. In the ensuing claims, where I refer to a pickling treatment or reagent, it will be understood that I contemplate the inclusion of etching treatments or reagents, and of such other chemical treatments or reagents as may be employed in the processing of metallic sheets.

Having thus described my invention in an exemplary embodiment, what I claim as new and desire to secure by Letters Patent, is:-

1. A process of pickling sheet metal, which comprises assembling sheets fiatwise upon a suitable support, separating said sheets from each other by an inert material in divided form, and. immersing said supporting means and said sheets in a pickling reagent.

2. The process of pickling metal articles, which comprises placing said articles on a suitable support and separating said articles one from another by a finely divided inert material, afterward immersing said articles and said support in a pickling reagent.

3. A process of pickling sheet metal, which comprises assembling metal sheets flatwise upon a suitable support and separating said sheets one from another by a relatively thin layer of inert separating substance in divided form, immersing said assembled sheets and support in a pickling reagent, and agitating said support and said sheets while immersed in said reagent.

4. A process of pickling metal articles, which comprises supporting said articles on a suitable supporting member and spacing said articles one from another by means of a finely divided inert substance, immersing said support and articles in a pickling reagent, and agitating said support and articles.

5. A process of pickling articles, which comprises supporting said articles upon a suitable supporting means and separating said articles from one another by means of layers of silica sand, afterward immersing said articles and said support, while said articles are so separated, beneath the surface of a pickling reagent,

*6; A process of pickling metal sheets which comprises loading said sheets horizontally upon a supporting member and positioning between each pair of sheets a relatively thin layer of silica sand so as to separate said sheets one from another, afterward immersing said sheets and said support, while said sheets are so separated, beneath the surface of a pickling reagent.

7. A process of pickling metal sheets which comprises loading said sheets horizontally upon a supporting member and positioning between each pair of sheets a relatively thin layer of silica sand so as to separate said sheets one from another, afterward immersing said sheets and said support, while said sheets are so separated, beneath the surface of a pickling reagent, and agitating said sheets by moving said support while in said reagent.

8. A process of pickling sheet metal, which comprises assembling sheets flatwise upon a suitable support, separating said sheets from each other by layers of an inert material in divided form, said layers being not less than substantially 1 inch in thickness, and immersing said supporting means and said sheets in a pickling reagent.

JAMES R. BOTI'OMS. 

